Art of vulcanizing rubber



in the later stages. ly desirable, as scorching or vulcanizing .on the Patented Apr. 23, 1935 I 2 UNITED STATES PATENT OFFICE ART or VULCANIVZING RUBBER Robert L. Sibley, Nitro, W. Va., assignor to The Rubber Service Laboratories Company, Akron, Ohio, a corporation of Ohio No Drawing. Application March 23, 1931,

Serial No. 524,761

'7 Claims.

This invention relates to the vulcanization of rubber by an improved process, wherein there is employed a member of a preferred class of compounds which improve the action of the accelera- ,tor used in the vulcanization process. More specifically, the preferred class of compounds act to retard the vulcanization inthe earlier stages of the process, but do ziot exertsuch retarding action andmay' ev'e'n accelerate the vulcanization This retarding efiect is highascertained by incorporating a small portion of Table I Modulus of elasticity in lbs/in. at No. parts elongation-s of Tensile Ultimate Time of cure and steam pressure dinitrolbs/infv elongation phenol at break percent 15 wins. at 10 lbs. steam per sq. in' I 85 .134 358 1, 565 990 Stock pitted 20 wins. at llbs. steam per sq. in 94 178 482 1, 955 970 30 mins. at 10 lbs. steam per sq. in .Q 137 302 1, 025 2, 540 900 125 232 769 2. 260 920 100 201 651 2, 100 950 90 mins at 20 lbs. steam per sq. in 257 636 2, 335 3, 530 780 p 248 624 2, 295 3, 440 785 229 549 2, 030 3, 370 795 V 120 mins. at 20 lbs. steam per sq. in 237 687 2, 460 4, 090 810 v 261 655 2, 325 3, 800 800 252 638 2, 293 3, 950 815 canized rubber product prepared in the manner specified above but containing no retarder.

As examples showing the use of the preferred class of compounds, a rubber mix was prepared in the well known manner comprising a V 7 Parts Pale crepe rubber 100 Zinc oxide Sulfur r r 3 The crotonaldehyde derivative of the reaction product of mercaptobenzothiazole and hexamethylenetetramine 0.6 ZA-dinitrophenol 0.1 and/or 0.2

The mix was then vulcanized by heating under various pressures and for various periods of time. The cured stock was then testedto determine its modulus and tensile strength under various degrees of elongation. The results of the tests of the rubber composition 'thus described are set forth in Table'I.

.. the compound or retarder in a rubber stock ofvulcanization characteristics, preferably in the presence of an accelerator, heating portions of the rubber compound thus formed for various periods of time and under various pressures, and comparing the modulus of elasticity and tensile strength of the vulcanized product so formed with the modulus and tensile figures of another vul- It is readily apparent from the data set forth above that the preferred class of compounds, for example, 2,4-dinitrophenol, retard the vulcanization process in the shorter timed cures, but do not appreciably retard this process on longer heat treatment at the higher pressures.

As further examples of the use of the preferred class of materials, the following six stocks, desig- Acetaldehyde derlya the reaction product of para-para-diamino-diphenyl-methane and mercaptobenzothiazole, prepared according to the method set forth in the co-pending U. S. patent application, Serial No. 456,808 new matured into U. S. Patent 1914,047

Diphony1guanidine.

Para-nitrophenol 2,6-dinitro-4chlorophcnol.

1'nitr0-2-naphthol 3,5-dinitroo-cresoL 3-nitro-p-eresol The results of the tests upon the above rubber stocks after curing are given in Table I11.

Table I I I Modulus of elasticity Steam in lbs/in. at elonga- Tensile Ultimate Cure prestions of at elongamius. sure A break tion lbs/in. lbs./in. percent 15 10 C 103 150 424 1, 740 1, 020 15 10 D 93 166 529 2, 285 985 15 10 E 105 186 516 1, 810 945 15 10 F 114 183 520 2, 045 970 10 A 121 252 820 2, 270 890 20 10 B 103 209 649 2, 220 055 20 10 O 169 495 2, 195 990 20 10 D 107 230 737 2, 690 50 20 10 E 206 050 2, 925 20 10 F 112 223 716 2, 360 930 30 10 A 95 283 1, 1 70 2, 640 840 30 10 B 139 294 1, 033 2, 970 900 30 10 C 139 273 925 2, 820 320 30 10 D 138 307 1, 060 3, 095 000 30 10 E 134 320 1, 155 2, 715 870 30 10 F 136 340 1, 145 2, 860 380 60 20 A 270 832 3, 260 4, 695 780 60 20 B 206 856 3, 300 4, 530 770 60 20 C 278 840 3, 320 4, 600 770 00 20 D 224 703 2, 935 4, 400 780 60 20 E 2.48 730 2, 890 4, 255 780 00 20 F 233 753 3, 140 4, 215 750 90 20 B 315 l, 010 3, S00 4, 770 745 90 2 U 270 950 3, 870 4, 380 725 90 20 D 304 915 3, 030 4-, 805 700 00 20 E 288 908 3, 600 4, 520 745 90 20 F 298 918 3, 7-40 4, 325 730 The results given in Table III show that the preferred class of compounds, for example parariitrophencl, 2,6-dinitrol-chlorophenol, l-nitro- E riaphthol, 3,fi-dinitro-ortho-cresol, and B-nitropara-'cresol, possess desirable retarding action on the curing process in the shorter timed and lower pressure cures, but show little or no retarding action in the longer timed and higher pressure cures, when present in a rubber stock of vulcanization characteristics.

Other nitro-aromatic hydroxides, for example, ortho-nitro-phenol, dinitro-naphthols, nitrosalicylic acids, nitro-resorcinols, nitro-chlorphenols, nitro-xylenols, and picric acid, may be employed in'the vulcanization of rubber as retarders in the manner hereinbefore described.

, This invention is not restricted to the use of the particular compounds given in the disclosure as examples, nor is it restricted to the use of the preferred class of compounds in the particular rubber mixes herein described. The invention is imite'd only by the claims attached hereto as part of the present application.

What is claimed is:

1. The process of retarding the vulcanization of. rubber which comprises heating a mixture of rubber, sulfur and an accelerator comprising an aliphatic aldehyde derivative of areaction prodct of an organic and a mercaptobenzothiazole in the presence of a dinitrophenol as a retarder of the accelerating action thereof.

2. The processor retarding the vulcanization of rubber which comprises heating amixture of rubber, sulfur and an accelerator comprisingan a iphatic aldehyde derivative of a reaction prod uct of an organic base and a mercaptobenzothiaable in the presence of 2,4-dinitrophenol as a retarder of the accelerating action thereof. 1

3. The process of retarding the vulcanization of rubber which comprises heating a mixture of rubber, sulfur and an accelerator comprising an aliphatic aldehyde derivative of a reaction product of an organic base anda mercaptobenzothiazole in the presence of a nitrophenol as a retarder of the accelerating action thereof 4. The process of retarding the vulcanization of rubber which comprises heating a mixture of rubber, sulfur and an'accelerator comprising an aliphatic aldehyde derivative of a reaction product of an organic base and mercaptobenzothiazole in the presence of a 'nitroph'ehol as a 'r'eta'rder of the accelerating action thereof.

5. The process of retarding, the vulcanization of rubber which comprises heating a mixture of rubber, sulfur and an accelerator comprising an aliphatic aldehyde derivative oi a. reaction prodnot of an organic base and mercaptobenzothiazole in the presence of 'a dinitrophenol as a retarder of the accelerating action thereof. .1 l.

6. The process or" retarding the vulcanization of rubber which comprises heating a mixture of rubber, sulfur and an accelerator comprising an aliphatic aldehyde derivative of a reaction product of an organic base and mercaptobenzothiazole in the presence of'dinitrophenol as a retarder 6f the accelerating action thereof.

'7. The process of retarding the vulcanizationof rubber which comprises heating a mixture of rubber, sulfur and an accelerator comprising the crotonaldehyde derivative of the reaction product of mercaptobenzothiazole and hexamethylenetetramine in the presence of 2,4-dinitrophenol as a retarder of the accelerating action thereof.

ROBERT L. SIBLEY. 

